Minimally invasive surgical procedures including, for example, endoscopic, laparoscopic, and arthoscopic procedures, allow a surgeon to perform a complex surgical procedure with minimal incisions into the skin and tissue surrounding a particular body cavity or anatomical region. In order to gain access to a body cavity, it is often necessary to puncture and cannulate the body cavity using a surgical access device such as a trocar. A trocar assembly generally includes a trocar housing with a cannula extending therefrom and a trocar obturator that is inserted through the cannula. In use, the trocar cannula, with the obturator extending therethrough, is pierced through the skin to access a body cavity. To penetrate the skin, the distal end of the trocar cannula is placed against an incision in the skin and pressure is applied to the proximal end of the trocar to force the sharp point of the obturator through the skin until it enters the targeted body cavity. The obturator can then be withdrawn, leaving the cannula as an access way to the targeted body cavity.
Generally, the proximal end of the trocar cannula is joined to a trocar housing that defines a chamber having an open distal end portion in communication with the interior lumen defined by the trocar cannula. The trocar oburator, as well as other elongated surgical instruments or tools, axially extend into and are withdrawn from the trocar cannula through the proximal end portion of the chamber defined by the trocar housing.
In use, it is important to maintain a substantially closed environment during insertion or withdrawal of instruments through the trocar assembly so as to preserve sterility of the treatment site in addition to preventing the escape of liquids and/or insufflation gas. Typically, a seal element is disposed within the housing in an attempt to provide such an environment. However, if an instrument is delivered off-axis relative to the cannula, the effectiveness of the seal may diminish, as off-axis delivery results in a disproportionate force being applied to one portion of the seal. This can result in non-uniform deformation of the seal which can reduce the seal's ability to effectively engage an outer surface of an instrument thereby resulting in contamination of the site and/or escape of liquids and/or insufflation gas from the cannula. Seal deformation can also be caused by inserting an instrument with a relatively large diameter through a seal having a relatively small diameter. In addition to deforming the seal, forcing a large diameter instrument through a relatively small diameter seal can result in a significant increase in the normal force subjected to the shaft of the instrument. The surgeon feels this increased force as increased drag or resistance to the instrument insertion/movement.
Accordingly, there remains a need for devices and methods configured to allow for the efficient and reliable delivery of a surgical instrument to a treatment site.